1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention relates to apparatus and methods for performing intralumenal procedures using catheters which can impart vibratory energy to a blood vessel or other body lumens being treated.
Despite the growing sophistication of medical technology, vascular (blood vessel) diseases, such as acute myocardial infarction (heart attack) and peripheral arterial thrombosis (blood clots in leg arteries), remain a frequent, costly, and very serious problem in health care. Current methods of treatment, often expensive, are not always effective. In the U.S. alone, the cost of treatment and support and the loss of productivity due to vascular diseases together exceed $40 billion per year.
The core of the problem is that diseased sites within the blood vessels narrow and eventually become completely blocked as a result of the deposition of fatty materials, cellular debris, calcium, and/or blood clots, thereby blocking the vital flow of blood. Current treatments include drugs, interventional devices, and/or bypass surgery. High doses of thrombolytics (clot-dissolving drugs) are frequently used in an effort to dissolve the blood clots. Even with such aggressive therapy, thrombolytics fail to restore blood flow in the affected vessel in about 30% of patients. In addition, these drugs can also dissolve beneficial clots or injure healthy tissue causing potentially fatal bleeding complications.
While a variety of interventional devices are available, including angioplasty, atherectomy, and laser ablation catheters, the use of such devices to remove obstructing deposits may leave behind a wound that heals by forming a scar. The scar itself may eventually become a serious obstruction in the blood vessel (a process known as restenosis). Also, diseased blood vessels being treated with interventional devices sometimes develop vasoconstriction (elastic recoil), a process by which spasms or abrupt reclosures of the vessel occur, thereby restricting the flow of blood and necessitating further intervention. Approximately 40% of treated patients require additional treatment for restenosis resulting from scar formation occurring over a relatively long period, typically 4 to 12 months, while approximately 1-in-20 patients require treatment for vasoconstriction, which typically occurs from 4 to 72 hours after the initial treatment.
The use of vibratory energy, typically in the ultrasonic range, has been proposed both to mechanically disrupt clots and to enhance the intravascular delivery of drugs to dissolve clots and inhibit restenosis. Vibrational energy may be delivered intravascularly using specialized catheters having a typically ultrasonically vibrating surface at or near their distal ends.
While highly promising, prior vibratory catheter designs have not always been able to provide the directions, modes, strengths, and other energy characteristics which are required or optimized for clot disruption or drug delivery. Specifically, prior vibratory catheters have not always been able to provide desired levels of mechanical disruption when the oscillating elements of the catheter are immersed in viscous fluid. This is especially true of catheters having smaller vibrational transducers which can reach areas in the vasculature or other body lumens unaccessible to catheters using larger transducers or vibrational generators located outside of the body. Furthermore, devices with external generators suffer from energy losses at all catheter bending points, resulting in variable and unpredictable amounts of vibrational energy at the catheter tip.
It would be desirable to provide improved devices, systems, and methods for treating vascular and other lumenal diseases, particularly stenotic diseases which occlude the coronary and other arteries. In particular, it would be desirable to provide novel vibratory catheter configurations using a plurality of vibratory oscillators capable of providing desired levels of mechanical disruption and/or fluid mixing. Such catheter configurations should be compatible with conventional catheter designs, such as angioplasty catheters, drug delivery catheters, perfusion catheters, and atherectomy catheters, but should also be useful as stand-alone devices intended to disrupt clot in blood vessels and perform other procedures in different body lumens. At least some of these objectives will be met by the catheter designs described and claimed hereinafter.
2. Description of the Background Art
Catheters having ultrasonic elements with the capability of delivering thrombolytic and other liquid agents are described in U.S. Pat. Nos. 5,362,309; 5,318,014; 5,315,998; 5,197,946; 5,380,273; 5,344,395; 5,342,292; 5,324,255; 5,269,297; 5,267,954; 4,808,153; 4,692,139; and 3,565,062; in WO 90/01300; and in Tachibana (1992) JVIR 3:299-303. See, in particular, FIGS. 6A and 6B of U.S. Pat. No. 5,197,946, which disclose a cantilevered transducer designed for non-bending actuation. A catheter system having a pair of spaced-apart balloons with a coiled piezoelectric strip therebetween is described in U.S. Pat. No. 5,279,546. Catheters having elongate ultrasonic transmission elements and inflatable cuffs are described in U.S. Pat. Nos. 5,397,301; 5,304,115; and 4,870,953. A tunneling catheter having a radiofrequency, laser, or ultrasonic active distal end disposed within an angioplasty catheter is described in EP 189 329. An atherectomy catheter having an ultrasonically enhanced blade disposed adjacent an asymmetrically mounted balloon is described in U.S. Pat. No. 5,085,662. Phonophoresis transducers disposed within porous, inflatable balloons are suggested in U.S. Pat. Nos. 5,286,254 and 5,282,785. A rigid ultrasonic probe intended for treating vascular plaque and having fluid delivery means is described in U.S. Pat. No. 3,433,226. An ultrasonic transmission wire intended for intravascular treatment is described in U.S. Pat. No. 5,163,421 and Rosenschein et al. (1990) JACC 15:711-717. Ultrasonic enhancement of systemic and localized drug delivery is described in U.S. Pat. Nos. 5,267,985; and 4,948,587; in WO 94/05361 and WO 91/19529; in JP 3-63041; and Yumita et al. (1990) Jpn. J. Cancer Res. 81:304-308. An electrosurgical angioplasty catheter having ultrasonic enhancement is described in U.S. Pat. No. 4,936,281. An infusion and drainage catheter having an ultrasonic cleaning mechanism is described in U.S. Pat. No. 4,698,058. Angioplasty balloon catheters having axial blade atherectomy, ultrasonic imaging, and rotary blade atherectomy devices at their distal ends are described in U.S. Pat. Nos. 5,053,044; 5,117,831; and 5,181,920, respectively. Ultrasonic imagery catheters having multiple transducers arranged in a phased array are described in U.S. Pat. No. 3,938,502 to Bom.
The present application is related to co-pending applications assigned to the assignee of the present application having the following Ser. Nos. 08/565,575; 08/566,740; 08/566,739; 08/708,589; and 08/867,007.
The full disclosures of each of the above listed U.S. patents and co-pending applications are hereby incorporated herein by reference.